Group B Streptococcus (Streptococcus agalactiae) has recently been identified as the leading cause of meningitis among neonates and young infants. A conservative estimation [C. J. Baker, J. Infectious Diseases, 136, No. 1, 137 (1977)] indicates that about 12,000 to 15,000 infants will be affected annually. Half of them will die. Those who survive may develop fatal neurological sequelae that often progress too far to be arrested by antibiotic treatments. For this reason, the immunological, preventive approach as embodied in vaccination of Group B streptococcal type-specific polysaccharides has evolved as one of the most important aspects for future control of the disease. In addition, antibody specific to type I.sub.a Streptococcus agalactiae has recently been found in the glands of bovine immunized with killed or live vaccine, indicating that Group B streptococcal type-specific polysaccharides may be important in vaccination against mastitis in dairy mammals, for example, dairy cattle.
Group B streptococcal antigens are generally classified into five serotypes (I.sub.a, I.sub.b, I.sub.c, II and III) based on capillary precipitin tests with hydrochloric acid-extracted antigens and type-specific hyperimmune rabbit antisera.
Although later studies have shown chemical compositions indicating structures quite different from those reported originally, the same serological classification, i.e., I.sub.a, I.sub.b, I.sub.c, II and III for streptococcal polysaccharides, are still being followed. For example, type-specific polysaccharides isolated via HCl-treatment of whole organisms were reported to contain rhamnose, glucosamine, and galactose, while type-specific polysaccharides prepared by TCA (trichloroacetic acid) extraction contained an additional antigenic determinant, sialic acid. Furthermore, structural difference may also arise from variation of fermentation conditions. Thus Group B Streptococcal polysaccharides isolated by identical methods from organisms grown in the presence of excess glucose has been found to contain no rhamnose as previously reported.
The present invention is related to novel Group B streptococcal polysaccharide types I.sub.a, I.sub.b, II and III, all of which contain galactose, glucosamine, glucose, and sialic acid. They are structurally distinguishable from those reported earlier as a result of variation in fermentation conditions, methods of isolation and purification.
Accordingly, it is an object of the present invention (1) to provide highly purified antigenic Group B streptococcal polysaccharide types I.sub.a, I.sub.b, II and III of novel structures; (2) to provide a vaccine for neonates or infants against Group B Streptococcus infections, for example, meningitis, containing at least one of the novel Group B streptococcal polysaccharides; (3) to provide a method for the prevention of neonatal diseases induced by Group B Streptococcus by vaccination of pregnant women or women of childbearing age; (4) to provide a novel method for the isolation and purification of the Group B streptococcal polysaccharides; (5) to provide a vaccine containing one or more of the type-specific Group B streptococcal polysaccharides for protection against masititis in dairy mammals; (6) to provide a method for protection against Group B Streptococcus infections by passive vaccination of patients with impaired immune system; and (7) to provide a method for protection against mastitis in dairy mammals by passive vaccination.